Nanoscale three-dimensional battery architecture

ABSTRACT

A three-dimensional nanobattery formed by individually wiring nanostructured electrodes and combining them with an electrolyte. Short, capped nanotubes termed ‘nanobaskets’ are formed by sputtering coating onto nanoporous templates. Metallic nanowires are grown by electrochemical deposition from the nanobaskets and through the template, making electrical contact with each nanobasket electrode. The same procedure can be used to fabricate both a battery anode and a battery cathode. A thin layer of electrolyte is placed between the two nanobasket electrodes, and electrical contact is made through the nanowires.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/695,835, filed Jan. 28, 2010, which claims priority to U.S.Provisional Patent Application Ser. No. 61/148,671, filed Jan. 30, 2009and is a continuation-in-part of U.S. patent application Ser. No.11/383,146 filed May 12, 2006, which claims priority to U.S. ProvisionalPatent Application Ser. No. 60/681,222 filed May 13, 2005, each of whichis incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with U.S. Government support under theDepartment of Defense, Army Research Office, DEPSCoR Grant No.W911NF-07-1-0398, the National Science Foundation Prime Agreement No.EPS-0447262. The U.S. Government has certain rights in the invention.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGAPPENDIX

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to nanoscale three-dimensional batteryarchitecture which can accommodate various combinations of new electrodematerials, electrolytes and wiring configurations in order to optimizebattery performance, and more particularly to a three-dimensionalnanobattery system having individually wired nanostructured anode andcathode electrodes with conductive nanowires and a thin, intermediatelayer of an electrolyte.

2. Description of the Related Art

The potential of nanotechnology to provide new technologicalbreakthroughs is the object of much current attention. Nanostructuredmaterials have the potential for enhanced properties and efficiencyimprovements in virtually every area of science and technology throughenhanced surface areas and quantum-scale reactions. This disclosuredeals with the formation of novel nanoscale structures that havenumerous potentially important applications.

An example of an application for nanotube structures is found inAssignee's U.S. Pat. No. 6,586,133 for “Nano-Battery Systems” issuedJul. 1, 2003. The patented disclosure is directed to nano-batteries andmicro-batteries as well as their manufacture and use. Porous substratetechnology is utilized wherein the substrate has a plurality of holes orpores that range in diameter between ten (10) micrometers to one (1)nanometer (nm).

Nanoscale or microscale deposition of particles by a sputtering processis also known. The process of sputtering may be defined as the ejectionof particles from a condensed-matter target due to the impingement ofenergetic projectile particles. Operatively, the source of coatingmaterial, referred to as the target, is mounted opposite to the sample,in this case a porous substrate in a vacuum chamber. The most commonmethod of generating ion bombardment is to backfill the evacuatedchamber with a continual flow of gas and establish a glow discharge,indicating that ionization is occurring. A negative potential applied tothe target causes it to be bombarded with positive-ions while thesubstrate is kept grounded. Impingement of the positive-ion projectileresults in ejection of target atoms or molecules and their deposition onthe substrate.

One of the most useful characteristics of the sputtering process is itsuniversality: virtually any material is a coating candidate. Sputteringsystems assume an almost unlimited variety of configurations, dependingon the desired application. DC discharge methods are often used forsputtering metals, while an RF potential is used for less conductivematerials. Ion-beam sources can also be used. Targets may be elements,alloys, or compounds, in either doped or undoped forms, and can beemployed simultaneously or sequentially. The substrate may beelectrically biased so that it too undergoes ion bombardment. A reactivegas may be used to introduce one of the coating constituents into thechamber, i.e. oxygen to combine with sputtered tin to form tin oxide(reactive sputtering).

A nanostructure fabricated by RF sputtering of barium strontium titanate(BST) on porous alumina substrates suggests that the sputtered materialdoes not penetrate into pores, but rather preferentially gathers alongthe continuous circular edge of pore openings. These types of sputteredmetal structure or “antidots” are not partially or complete capped, arenot layered, are formed only from metals, and are not used to assembleany type device.

Nanotubes and other nanostructures may be formed as large arrays, and inthis form are often referred to as nanoporous or mesoporous structures.“Meso-porous” tin oxide structures have been created using surfactanttemplating techniques. The resultant material, however, consists ofmaterial containing irregular nanopores averaging about two (2) nm insize, without long-range order. These nanoporous or mesoporus structurescannot be formed in large arrays of tunable pore sizes, which developwall height as well as porosity, and also cannot be partially orcompletely capped to form a nanobasket structure.

Accordingly, it is desirable to produce a nanotube structure wherein atleast one end of a nanotube is partially or completely closed or coveredover so that the nanotube forms a nanobasket.

It is further desirable to use sputter deposition techniques to createpartially or completely capped and/or layered nanotube structure, whichopens a wide range of potential applications.

It is still further desirable to utilize a substructure of very smallnanoparticles, i.e., the walls and caps of the basket are themselvescomposed of nanoparticles ten (10) nm and less in size. Numerousscientific studies attest to the importance of nanoparticulate grainsize in performance characteristics of electronic, optical, andcatalytic devices.

It is yet further desirable to form a large array of nanobaskets as ananoporous architecture, such as for use in battery systems.

The assembly of individual nanostructured components into athree-dimensional battery system has been proposed as the means topromote ion diffusion in electrode materials by substantially increasingthe effective electrode surface area to improve energy per unit areacharacteristics and promote a high rate charge/discharge capacity. Suchfeatures should enhance general battery performance, but they are ofparticular importance for thin film batteries and nanobatteries able topower proposed micro and nano electromechanical systems (MEMS and NEMS).Recent work on three-dimensional architectures for improved performanceincludes rods or “posts” connected to a substrate, graphite meshes andfilms of cathode, electrolyte and anode materials lining microchannelsin an inert substrate.

The nanoscale three-dimensional battery architecture disclosed hereinrepresents a novel approach from other proposed solutions by focusing ona negative space (the hollow portion within the nanobaskets) rather thanon a positive-space structure such as a rod, post, mesh or film. Whilemultiple three-dimensional battery architectures have been proposed, noprior configurations are based upon the individual wiring of hollownanobaskets nor has a working three-dimensional nanobattery beenclaimed.

It is therefore desirable to provide a three-dimensional nanobatteryformed by individually wiring nanobasket structured electrodes andcombining them with an electrolyte. Short, capped nanotubes, i.e.,nanobaskets, may be formed by RF-magnetron sputtering onto nanoporoustemplates, and metallic nanowires are grown, such as by electrochemicaldeposition, from the nanobaskets. The same procedure can be used tofabricate both a battery anode and a battery cathode, and a thin layerof electrolyte is placed between the two nanobasket electrodes. Thenanobattery circuitry may be completed by contacting the ends of thenanowires opposing the electrolyte with a conductor, such as a metalplate.

It is further desirable to provide a three-dimensional nanobatteryarchitecture that promotes ion diffusion in electrode materials bysubstantially increasing the effective electrode surface area to improveenergy per unit area characteristics and promote a high ratecharge/discharge capacity.

It is still further desirable to provide a nanoscale three-dimensionalbattery architecture for thin film batteries and nanobatteries, whichwould be able to power proposed micro- and nano-electromechanicalsystems (MEMS and NEMS), or used in massive arrays in place ofconventional batteries.

It is yet further desirable to provide a nanoscale three-dimensionalbattery architecture based upon individual wiring of hollownanostructures and that represents a robust nanoarchitecture thataccommodates a variety of electrode and electrolyte types.

SUMMARY OF THE INVENTION

In general, in a first aspect, the invention relates to a method ofproducing a three-dimensional nanobattery by providing a substratehaving at least one pore, depositing at least one material alongcontinuous edges of the pore to form a nanobasket, depositing at leastone conductive material within the nanobasket and through the substrateto form a nanowire, and providing a layer of electrolyte in electricalcontact with the nanobasket. The method may further include the steps ofproviding a cathode substrate having a plurality of pores, each of thepores having a continuous edge at a surface of the cathode substrate;depositing the at least one material along the continuous edge of eachof the pores of the cathode substrate forming a plurality of cathodenanobaskets; depositing the at least one conductive material within thecathode nanobaskets and through the pores of the cathode substrate toform a plurality of nanowires connected to the cathode; providing ananode substrate having a plurality of pores, each of the pores having acontinuous edge at a surface of the anode substrate; depositing the atleast one material along the continuous edge of each of the pores of theanode substrate forming a plurality of anode nanobaskets; depositing theat least one conductive material within the anode nanobaskets andthrough the pores of the anode substrate to form a plurality ofnanowires connected to the anode; providing the layer of electrolyteintermediate of the cathode nanobaskets and the anode nanobaskets; andmaking electrical contact with the cathode nanowires and the anodenanowires.

The step of depositing the at least one material along the continuousedges of the pore of the method may be accomplished by sputter-coating,such as direct current sputter-coating, radio frequency sputter-coating,magnetron sputter-coating and reactive sputter-coating, chemical vapordeposition or pulsed laser method. At least one additional material mayalso be deposited to form a layered nanobasket structure.

In general, in a second aspect, the invention relates to athree-dimensional nanobattery having a nanoporous substrate, ananobasket, a nanowire and a layer of electrolyte. The nanoporoussubstrate includes at least one pore, with each the pore having acontinuous edge at a surface of the substrate. The nanobasket isfabricated from clusters of material deposited on the continuous edge ofthe substrate, while the nanowire is fabricated from a conductivematerial through the nanobasket and the substrate. The layer ofelectrolyte is in contact with the nanobasket. The substrate may includea plurality of the pores, the nanobasket may include a plurality ofcathode nanobaskets and a plurality of anode nanobaskets, and thenanowires may be a plurality of nanowires, with the layer of electrolytebeing intermediate of the cathode nanobaskets and the anode nanobaskets.

The substrate of the nanobattery may be a conducting, non-conducting orsemi-conducting material, such as at least one of solid oxide,polymeric, ceramic, mineral or metallic materials or a polycarbonate,carbon, silica, silicon or alumina material. The material deposited toform the nanobasket may be a conducting, non-conducting orsemi-conducting material. Moreover, the material deposited to form thenanobasket may be an oxide, polymeric, ceramic, mineral or metallicmaterial, such as tin oxide, lithium cobalt oxide, zinc oxide, copperoxide, titanium oxide, titanium dioxide, vanadium pentoxide, magnesiumoxide, silicon dioxide, carbon, silicon, nichrome, and hydroxyapatite.The conductive material used to fabricate the nanowires may be anyconductive metal, such as copper or any electrically conducting polymer,such as poly(acrylonitrile). Additionally, the nanobattery may includeat least one additional material to form a layered cap over thenanobasket.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an electron microscope photograph of a stage in theprocess of the fabrication of nanobaskets by sputter deposition onporous substrates disclosed herein;

FIG. 2 illustrates a sequential stage in the process subsequent to thatshown in FIG. 1;

FIG. 3 illustrates a partial, sectional view of an electron microscopephotograph of a further subsequent stage of the process;

FIG. 4 illustrates a simplified, diagrammatic view an example cappedtubes utilizing multiple compositions to create a layered structure inaccordance with an illustrative embodiment of the fabrication ofnanobaskets by sputter deposition on porous substrates disclosed herein;

FIGS. 5, 6 and 7 illustrate subsequent, sequential stages in theformation of capped tubes of multiple compositions shown in FIG. 4;

FIG. 8 illustrates an electron microscope photograph of a sectional viewof a partially capped nanobasket in accordance with an illustrativeembodiment of the fabrication of nanobaskets by sputter deposition onporous substrates disclosed herein;

FIG. 9 illustrates an electron microscope photograph of a cappednanobasket utilizing multiple compositions to create a layered structurein accordance with an illustrative embodiment of the fabrication ofnanobaskets by sputter deposition on porous substrates disclosed herein;

FIGS. 10 through 13 illustrate potential applications of the fabricationof nanobaskets by sputter deposition on porous substrates disclosedherein;

FIG. 14 illustrates a transmission electron microscope photo of thegrains composing the nanobasket in accordance with an illustrativeembodiment of the fabrication of nanobaskets by sputter deposition onporous substrates disclosed herein;

FIG. 15 illustrates a perspective view of a three-dimensionalnanobattery in accordance with an illustrative embodiment of thenanoscale three-dimensional battery architecture disclosed herein;

FIGS. 16( a) through 16(d) show SEM images of the nanowiring of ananobasket structure in accordance with an illustrative embodiment ofthe nanoscale three-dimensional battery architecture disclosed herein;

FIG. 16( a) shows a nanobasket structure grown on a nanoporous membrane,wherein the dashed line shows the outline of the nanobasket; FIG. 16( b)shows the wired membrane with the nanowires running from thenanobaskets, through the nanoporous membrane so that electrical contactcan be made with a current collector; FIG. 16( c) has a highermagnification showing the nanowire extending into the nanobasket andmaking contact with the nanobasket (dashed line) where intimate contactwith the nanobasket electrode is made; and FIG. 16( d) shows the top ofthe nanobasket structure having a large surface area for electrolytecontact;

FIG. 17 illustrates a complex plane impedance plot or Nyquist plot ofthe nanobasket layer, obtained by contact through the nanowires, whilethe inset shows the high frequency region in increased detail; and

FIG. 18 is a graphical representation of the charge/discharge of thethree-dimensional nanobattery at 50 nA charge rate and 10 nA dischargerate.

Other advantages and features will be apparent from the followingdescription and from the claims.

DETAILED DESCRIPTION OF THE INVENTION

The devices and methods discussed herein are merely illustrative ofspecific manners in which to make and use this invention and are not tobe interpreted as limiting in scope.

While the devices and methods have been described with a certain degreeof particularity, it is to be noted that many modifications may be madein the details of the construction and the arrangement of the devicesand components without departing from the spirit and scope of thisdisclosure. It is understood that the devices and methods are notlimited to the embodiments set forth herein for purposes ofexemplification.

Referring to the figures of the drawings, wherein like numerals ofreference designate like elements throughout the several views, andinitially to FIG. 1 illustrating an electron microscope photograph of astage in the process of the formation of a nanoscale structure thatincludes capped nanotubes, termed “nanobaskets” by a sputter-coatingmethod on a porous substrate as the template for the structure. Thenanoporous substrate could be made from numerous materials whose surfaceenergy values are such that they are conducive to the formation ofnanobaskets. In one example, a substrate has a plurality of pores thatrange between ten (10) micrometers to one (1) nanometer (nm) indiameter. Various substrates could be used, e.g., either polymeric (suchas polycarbonate) or ceramic material (such as alumina oxide (Al₂O₃)).Nanoporous substrates of silicon or metallic porous structures couldalso be used. The substrate includes pores that could be created bylaser ablation, a chemical etching process, an electrochemical process,track etching, micro or nanolithography, contact lithography, chemicalself-assembly or by other methods. The length of the pores in thesubstrate itself has not been found to be critical to the nanobasketformation, and so could vary over any conceivable length range.

The nanoporous substrate could be made using several techniques. Oneinvolves the use of nanoporous anodized aluminum oxide substrates. Theprocess for making these substrates has been described in the literature(H. Masuda, K. Nishio and N. Baba, Thin Solids Films, 223, 1, (1993); H.Masuda and K. Fukuda, Science, 268, 1466 (1995); A.-P. Li, F. Muller, A.Birner, K. Neilsch, and U Gosele, Adv. Mater. 11, 483 (1999); I.Mikulska, S. Juodkazis, R. Tomasiunas, and J. G. Dumas, Adv. Mater. 13,1574 (2001)) and consists of applying an electrical potential to analuminum sheet while in an acid solution. Micro and nanolithographictechniques and other techniques such as X-ray-beam, electron-beam andion-beam lithography could be used. Microcontract printing could also beused to make the nanoporous substrate.

The nanobasket structure can be formed using sputter-coating techniques.This includes DC sputter-coating, RF sputter-coating and RF magnetronsputter-coating. Chemical reactive sputtering could also be used. Thestructure could also be formed using chemical vapor deposition or pulsedlaser methods.

At the surface of the substrate, the pores have a continuous edge, whichcould be of any relative geometric configuration. As a target materialis sputter-coated, nanoscale clusters of the material collectpreferentially on the continuous edge of the pores of the underlyingsubstrate. As the process of depositing material continues, it resultsin the gradual build-up of “walls” that effectively extend the porestructure with the target material to form a nanotube. The pore size ofthese nanotubes is dependent on the substrate's original pore structureand, therefore, their diameter can be varied by using substrates ofvarying pore sizes.

As the sputter-coating process is continued, it has been observed thatthe walls grow thicker as they grow taller so that they will eventuallytouch, capping over the pore spaces with deposited material to form thebase or end of a basket. Depending on the parameters used in thesputter-coating process, such as plasma gas concentration, power, targetmaterials, and underlying substrate, the pores can be made to cap atvarious lengths or heights from the substrate surface, ranging from tensto hundreds of nanometers. Capped nanoporous structures have heretobefore been difficult to synthesize and have different potentialapplication than open tubes.

FIG. 1 illustrates an electron microscope photograph of a stage in theprocess of the fabrication of a nanobasket by sputter deposition on aporous substrate in accordance with an illustrative embodiment of thefabrication of nanobaskets by sputter deposition on porous substratesdisclosed herein. FIG. 2 illustrates an electron microscope photographof approximately 400 nanometers of tin oxide sputtered onto an aluminasubstrate. It will be observed that the material is beginning to cap orclose over. FIG. 3 illustrates an electron microscope photograph of apartial cross-section of the photo shown in FIG. 2. The aluminasubstrate may be viewed with the tin oxide sputtered thereon to form thenanobaskets. FIG. 8 is an electron microscope photograph that shows thatas the structures begin to cap over, very small nanochannels are formedthat may also be of technical significance. Such nanochannels havepotential applications in the trapping of molecular species, confinementof DNA and RNA, specialized filtrations, and chromatographic analysis.This would be one example of a “partially capped” structure. Partiallycapped structures are created by stopping the sputtering process beforethe walls of the nanobasket have grown together to form a continuouscap. FIG. 9 illustrates an electron microscope photograph of a cappednanobasket utilizing multiple compositions to create a layeredstructure. FIG. 14 shows the nanograins that compose the walls and capof the nanobasket. The fact that the nanobasket architecture itselfcontains a substructure of nanograins is expected to further enhance theperformance of the nanobaskets.

Initial research indicates that the method is robust and can begeneralized to many materials of technological importance. Currentresearch has focused on metallic oxides, such as SnO₂, LiCoO₂, and TiO₂for which nanobaskets would be of importance in photovoltaic and batteryapplications. Copper oxide nanobaskets are of importance in catalyticoperations. Metal alloys, such as Nichrome, are useful for themanufacture of thermal devices. Even materials such as hydroxyapatite,the mineral closest in composition to bone, are amenable to thistechnique and have been observed to form nanobaskets. These materialsmay have important applications as bone mimics and tissue scaffolding.

The fabrication of nanobaskets by sputter deposition on poroussubstrates disclosed herein also allows the formation of nanobaskets ofmultiple compositions. The ability to create a layered structure istruly unique and allows for the straightforward and easy assembly ofnanodevices using appropriate selections of materials; for example,current collectors, electrodes, and semiconductors or layeredsemiconductors. A layered nanobasket system may made by sputtering afirst material, but stopping the sputtering at some desired point beforethe walls have grown thick enough to form a cap. A second material canthen be sputtered atop the first, continuing to extend the walls of thebaskets upward. Sputtering of this second material can continue untilcapping occurs, or it can also be stopped at a desired point before thewalls have grown together, and more layers can be added. Configurationsof up to five layers have so far been demonstrated. The number of layerspossible is dependent upon the materials and pore sizes used.

The nanobasket structures can be used as sputtered, remaining attachedto the substrate, or may be removed from the substrate by appropriatemechanical or chemical methods. The nanobasket structures can further beutilized by functionalization of their surfaces, attachment ofadditional catalytic materials, or by filling the pore spaces with adesired medium such as an electrolyte. Further, the nanobasketstructures can undergo heat-treatment as necessary for a desiredapplication.

The nanobasket structures and/or layers within them may be made fromdoped elements or compounds; for example, SnO₂ doped with Indium. Anexample of fabrication of a nanobasket from a single deposited materialand from multiple compositions to form a layered cap follows:

Example 1 of Single-Component Fabrication Using SnO₂

An anodized aluminum oxide (AAO) substrate is placed on the sample stageof an RF-magnetron sputtering system which is fitted with a tin oxide(SnO₂) target. A chamber is filled and flushed with argon gas, andsputtering is initiated under system conditions of 0.01 mbar argonpressure and 35 watts forward power. In accordance with the generallyrecognized principles of sputter depositions, SnO₂ is removed from thetarget and deposited onto the AAO substrate. Film thickness is monitoredusing a quartz crystal thickness monitor. When the desired thickness isreached, turning off the power halts the sputtering process.

Example 2 of Layered Fabrication Using Gold (Au) and Lithium Carbonate(LiCoO₂)

An anodized aluminum oxide (AAO) substrate is placed on the sample stageof an RF-magnetron sputtering system which is fitted with a gold (Au)target. The chamber is filled and flushed with argon, and sputtering isinitiated under system conditions of 0.01 mbar argon pressure and 35watts forward power. In accordance with the generally recognizedprinciples of sputter depositions, gold is removed from the target anddeposited onto the AAO substrate. Film thickness is monitored using aquartz crystal thickness monitor. When the desired thickness is reached,sputtering is halted and the chamber is opened. A new target of LiCoO₂is installed. The chamber is again filled and flushed with argon, andsputtering is initiated under system conditions of 0.01 mbar argonpressure and 35 watts forward power. LiCoO₂ is removed from the targetand deposited onto the gold layer previously deposited on the AAOsubstrate. Film thickness is monitored using a quartz crystal thicknessmonitor. When the desired thickness is reached, turning off the powerhalts the sputtering process.

FIGS. 4, 5, 6 and 7 illustrate simplified diagrammatic views of thesequential fabrication of capped nanostructures by sputter depositionutilizing multiple compositions. FIG. 4 illustrates the pores of thesubstrate prior to application of any sputter deposition. FIG. 5illustrates use of sputter deposition techniques to apply a metallicdeposit onto the edges or open ends of the nanotube structures. FIGS. 5,6 and 7 illustrate the sequential application of a metallic oxide ontothe metal layer previously deposited on the nanotube structure. As willbe observed, continued application of the metallic oxide results in thecapping over of the tubes.

Photovoltaic Device

The second concept involves using these nanostructures to makephotovoltaic devices 18 as shown in FIG. 10. In typical photovoltaicdevices, a transparent current collector must be used so that light maypass through it for interaction with the photovoltaic material. Usingthe layered structure formation in concept (1), a new type ofphotovoltaic 18 could be manufactured. The photovoltaic 18 would bemanufactured by first depositing 14 a conducting metal layer 12 on thenanoporous substrate 10. This layer will serve as a current collector12. A second layer of a photoactive semiconductor (photovoltaic layer)13 will be deposited and allowed to cap over. This structure is a verynovel component for a photovoltaic device. It has been shown thatnanoporous materials can serve as optical waveguides. (K. H. A. Lau,L.-S. Tan, K. Tanada, M. S. Sander, and W. Knoll, “Highly SensitiveDetection of Processes Occurring Inside Nanoporous Anodic AluminaTemplates: A Waveguide Optical Study,” Journal of Physical Chemistry,108, 10812 (2004)). The size of the pores in the nanoporous substrate 10can be of the appropriate size to interact with light such that theyfunction as a waveguide. This will facilitate the passage of light 11through to open pores of the noncoated side of the nanoporous substrate10. This light will be able to pass through the pores in the nanoporouscurrent collector 12 impinging on the capped photovoltaic material 13.The size of the pore and the curvature of the cap part of thenanobaskets could further accentuate the interaction of light by actingboth as an additional waveguide and a lens, further focusing the lighton the photovoltaic material 13 and enhancing performance. This would bea novel structure for a photovoltaic device. The completed photocell 18would be constructed by placing an electrolyte 15, complementaryelectrode 16, and a second current collector 17, respectively on thecapped side of the photovoltaic material 13.

Battery Systems

The third concept involves using a multilayered, nanobasketnanostructured material to make thin film battery systems as shown inFIG. 11. Again using the layered structure formation in concept (1), alayer of nanobaskets of an appropriate battery electrode material 21 aresputter-coated onto a nanoporous substrate 20. The nanoporous substrate20 and the nanobaskets 21 are filled with electrolyte 22 using capillaryaction to “pull” the electrolyte into the pores (as described inAssignee's U.S. Pat. No. 6,586,133) or other techniques. The oppositeside of the nanoporous substrate 20 would still have pores that areopen, but filled with electrolyte 23. One configuration of the batterywould now cover this end of the substrate with an appropriate electrodematerial forming a battery. Placing the electrode 23 on this side couldbe done by many methods including sputter-coating, spreading of pastesof composite electrode materials, etc. A current collector 24 would beaffixed to this electrode 23. This thin film battery would haveincreased performance because of the increased surface area of thenanobasket electrode and because of the enhanced performance ofelectrolyte materials confined in nanoporous materials. (SeshumaniVorrey and Dale Teeters, “Study of the Ion Conduction of PolymerElectrolytes Confined in Micro and Nanopores,” Electrochimica Acta, 48,2137 (2003)).

A second battery configuration as depicted in FIG. 12 would consist offirst placing a layer of current collecting material 31, such as ametal, by sputter-coating on the nanoporous substrate 30. This currentcollecting layer 31 is capped with nanobaskets 33 of an appropriatebattery electrode material. Using capillary action to “pull” theelectrolyte into the pores (as described in Assignee's U.S. Pat. No.6,586,133) or another appropriate technique, both the pores of thesubstrate 30 and those in the current collector 31 and the nanobaskets33 are filled with electrolyte 32. The opposite side of the nanoporoussubstrate would still have pores that are open, but filled withelectrolyte 34. Deposition of the complementary electrode 35 would againbe done by using sputter-coating. Because of the nanoporous substrate33, a nanobasket electrode layer 34 would be formed. This configurationwould benefit from having two electrodes 32 and 34 both having ananobasket configuration. This thin film battery would have increasedperformance because of the increased surface area of both of thenanobasket electrodes 32 and 34 and because of the enhanced performanceof electrolyte materials confined in nanoporous materials. (SeshumaniVorrey and Dale Teeters, “Study of the Ion Conduction of PolymerElectrolytes Confined in Micro and Nanopores,” Electrochimica Acta, 48,2137 (2003)).

As shown in FIG. 13, another configuration would allow the in situformation of a battery anode in a nanostructured thin film battery. Thisconfiguration consists of first depositing a first layer of currentcollecting material 41 by sputter-coating on a nanoporous substrate 40.This layer 41 is not allowed to cap. This current collecting layer 41 isthen capped with nanobaskets 42 of an appropriate battery cathodematerial by deposition by sputter-coating. This material must containmetal ions of the same composition of the anode desired to be formed. Byusing capillary action to “pull” the electrolyte into the pores (asdescribed in Assignee's U.S. Pat. No. 6,586,133) or other appropriatetechniques, the pores of the substrate 40 and those in the currentcollector 41 and the nanobaskets 42 can be filled with electrolyte 43. Asecond current collector 44 would be placed on top of the nanobasketelectrode layer 42. The opposite side of the nanoporous substrate wouldstill have pores that are open, but filled with electrolyte 43. At thispoint a thin film battery could be formed by in situ deposition of ananode 45. The “in-situ” formation of an electrode has been described inthe literature. (B. J. Neudecker, N. J. Dudney, and J. B. Bates,“Lithium-Free Thin-Film Battery with In Situ Plated Li Anode,” Journalof the Electrochemical Society, 147 517 (2000)). This technique isapplied to our nanostructured system by applying an appropriate current46 to the two current collectors 41 and 44 drawing metal ions from thecathode layer 42 and through the electrolyte 43 present in thenanopores. This will result in electrochemical plating of the metalanode 45 onto the current collector 41 that closest to the nanobasketopenings. This plated metal would be the anode 45 formed in situ. Sincethis anode 45 would be in very close proximity to the nanobasket 42,cathode material, it would enhance performance. Since the anode 45 isdeposited in situ and is not exposed to air, the anode 45 is less likelyto be degraded by air exposure, thus eliminating a major problem in thedevelopment of thin-film lithium batteries. Once again, this thin filmbattery would also have increased performance because of the increasedsurface area of the nanobasket electrode and because of the enhancedperformance of electrolyte materials confined in nanoporous materials.(Seshumani Vorrey and Dale Teeters, “Study of the Ion Conduction ofPolymer Electrolytes Confined in Micro and Nanopores,” ElectrochimicaActa, 48, 2137 (2003)).

Nanoscale Three-Dimensional Battery Architecture

One of the difficulties in creating effective three-dimensionalarchitectures lies in the conflicting geometric goals for high capacityand low resistance. (W. Long Jeffrey, B. Dunn, R. Rolison Debra, S.White Henry, Chem Rev, 104 (2004) 4463-4492). When utilizing micro-rodsor micro-plates of electrode material extending from a substrate intothe electrolyte, for example, capacity increases as the length, L, ofthe rods or plates is increased but electronic resistance also increaseswith L, limiting overall system performance. In many three-dimensionalarchitectures, a tradeoff between efficient ion diffusion and electronconduction must be made. The nanoscale three-dimensional batteryarchitecture described herein addresses these concerns by combining ananostructure that presents a high surface area for ion diffusion withnanoscale wiring to reduce ohmic resistance.

The individual wiring of nanobaskets has distinct benefits. Long et al.have used the dimensionless number, U, described in the equation below,to analyze electrode performance.

$\begin{matrix}{U = {\left( \frac{w^{2}}{L^{2}} \right)\left( \frac{\mu}{\sigma} \right)\left( \frac{1}{C} \right)}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$where w is either the diameter of rods or the thickness of plates in athree-dimensional microelectrode architecture, L is the length of therods or height of the plates, μ is the ionic mobility of the cations inthe electrolyte, σ is the electronic conductivity of the electrodematerial and C is the volumetric energy capacity. U serves to describethe uniformity with which the electrode is utilized. The smaller Ubecomes the more uniform is the current distribution along theelectrode.

A hollow structure, e.g., a nanobasket, is one of the best ways ofovercoming these geometrical limitations, improving the utilitycoefficient (U) of the electrode by 50% based upon geometricalconsiderations alone. The nanoscale three-dimensional battery disclosedherein is the only system known to utilize a hollow (negative space)nanostructure. Further improvements are based upon the intimate contactbetween the nanowires and the nanobasket electrode, thereby providing ahigh effective σ value. Additionally, the L term in Equation 1 ismaximized by the exterior surface of the nanobaskets, which would be thesurface in contact with the electrolyte in a three-dimensional batteryconfiguration. This exterior surface, which can be thought of as atopography of upside-down nanobasket ‘caps,’ presents a high surfacearea for electrolyte contact. FIG. 16( d) is an SEM image of this highsurface area demonstrating its highly roughened nature, with fissuresand crevices between the individual nanobaskets caps readily seen. Boththe curved nanobasket caps and the fissures between them make a highsurface area available for electrolyte contact, which will enhance iondiffusion into the electrode material and complement the augmentedelectronic conduction resulting from the nanowires inside thenanobaskets.

Nanobasket Electrodes

As fully described above in relation to fabrication of nanobaskets bysputter deposition on porous substrates, the nanostructured oxide filmsmay be constructed by RF-magnetron sputtering onto a nanoporous anodizedaluminum oxide (AAO) substrates. During sputtering, thickened columnargrowths form around the pores of the substrate, essentially extendingthe pores with the oxide material. The diameter of these columns isdependent on the diameter of the substrate pores, and they grow thickeras they extend upward, eventually growing together to form caps over theempty pore spaces, i.e., “nanobaskets.” (P. L. Johnson, D. Teeters,Solid State Ionics, 177 (2006) 2821-2825). Raman spectroscopy hasrevealed that the nanobaskets have a substructure of coalescednanoparticles whose size is on the scale of 2 nm. It has beendemonstrated that electrodes composed of such small nanoparticles showbetter cyclability (J. O. Besenhard, J. Yang, M. Winter, J. PowerSources, 68 (1997) 87-90; I. A. Courtney, J. R. Dahn, J. Electrochem.Soc., 144 (1997) 2045-2052) and a greater initial specific batterycapacity. (J. S. Sakamoto, C. K. Huang, S. Surampudi, M. Smart, J.Wolfenstine, Mater. Lett., 33 (1998) 327-329).

In preparation of the nanobattery, layers of electrode materials, and/orlayered systems of a metal plus the electrode materials were sputtercoated onto porous substrates, as shown in FIGS. 16( a) and 16(c). Arange of electrode materials, metals, and substrates can be used.

Nanowiring of Nanobasket Electrodes

The nanoscale three-dimensional battery architecture utilizesindividually wiring the nanobaskets with copper wires to allow intimateelectrical contact with the electrode material. Nanowired electrodes ofboth anodic and cathodic materials have been fabricated, and electricalcontact with them has been demonstrated by AC Impedance spectroscopy, asillustrated in FIG. 17.

A standard, three-probe electrochemical cell was used to grow thenanowires in porous substrates. AAO substrates which had been sputteredwith 100 nm of gold and 500 nm of SnO₂ or LiCoO₂ were placed onto aplatinum dish so that the nanobaskets were in contact with the platinumdish, which served as the working electrode. The dish was filled with athin layer of an aqueous solution 0.5 M in CuSO₄ and 0.1 M in boricacid, filling the pores of the substrate. The bare side of the substratewas brought into contact with another platinum surface, which acted asthe counter electrode. A standard Calomel electrode functioned as thereference electrode. Copper nanowires were grown from the nanobasketelectrode layers and into the 200 nm pores, ultimately extending throughthe entire 60 micron thickness of the AAO membrane, using a DC voltageof −0.15 V applied for 17 seconds from a potentiostat.

Nanowires may also be made by solution chemistry, by sol-gel processes,by electrophoretic deposition, electroless deposition, vapor-phasedeposition, thermal evaporation, self-assembly, photoreduction, webcoating and doctor blade techniques. The goal of prior published workhowever, was merely to grow wires alone. The application herein, ofgrowing wires from an electrode structure and through the length of themembrane in order to make electrical contact, is unique and novel. Asdiscussed above, copper nanowires were grown from the nanobasketelectrode layers and into the 200 nm pores, ultimately extending throughthe entire 60 micron thickness of the AAO membrane, using a DC voltageof −0.15 V applied for 17 seconds in an aqueous solution 0.5 M in CuSO₄and 0.1 M in boric acid. AAO membranes with 200 nm pore sizes, formingcopper nanowires of the same diameter, were utilized since coppernanowires smaller than 100 nm diameter have a higher resistance due tobeing close to the mean free path of electron diffusion in copper metal.(W. Steinhogl, G. Schindler, G. Steinlesberger, M. Traving, M.Engelhardt, J. Appl. Phys., 97 (2005) 023706/023701-023706/023707; K.Hinode, Y. Hanaoka, K.-I. Takeda, S. Kondo, Jpn. J. Appl. Phys., Part 240 (2001) L1097-L1099). Enough wires were formed, however, to be clearlyvisible in the cleaved cross-section when examined in the scanningelectron microscope, as can be seen in FIG. 16( c), and conclusive proofthat the electrical contact could be made with through the wires to theelectrode was provided by AC impedance spectroscopy. (FIG. 17). It willbe appreciated that in addition to copper, any other conductivemetal/material may be used as the nanowires, for example, anelectrically conducting polymer, such as poly(acrylonitrile).

Thin-Film Electrolyte

Once both anodic and cathodic nanowired-nanoelectrodes have beenfabricated, an electrolyte layer can be placed between the twoelectrodes. One configuration would be the thinnest layer of electrolytepossible; as long as the electrolyte forms a continuous layer coveringthe electrodes and is thick enough to prevent significant electronicconduction, which would “short” the battery. However, the thinner theelectrolyte, the less distance the ion will have to traverse through theelectrolyte. Thus, the shorter the distance, the less resistance theelectrolyte will contribute to the battery, thereby making the batteryfunction with less IR drop and enhance battery performance. Therefore,ion conduction is at its greatest with the thinnest layer of electrolytepossible, such as a thickness from below approximately one (1) nm tomicrons in thickness. During the charging and discharging of thebattery, ions must move into out of the electrolyte and electrodes.Thus, an increased number of ions will readily be transferred duringthis process with an increased electrolyte surface area, and therebyenhancing ion conduction.

The electrode material could be a thin layer of liquid electrolyte or athin layer of solid electrolyte. The liquid electrolyte could be aqueousor nonaqueous in nature. A solid electrolyte could include oxides,ceramics or polymer electrolytes. Electrode materials could also bemultiple layers of solid and/or liquids or composite materials composedof various liquids and/or various solids or particles.

This thin layer could be placed on the electrodes by several methods,including but not limited to DC sputter coating, RF magnetron sputtercoating, vapor deposition, spin coating and chemical self-assembly toform molecular level layers. Liquids and solutions could also be placedbetween the two electrode layers by placing micro- or nanoparticleinsulation spacers between the two electrode structures and allowingcapillary action to pull the liquids or solvents between the twoelectrodes. These spacers could be placed on one or both electrodesurfaces, such as by dusting the surface with insulating micro- ornanoscale particles that would serve as the spacers, and then the twoelectrodes would be placed together. Dispersed insulating particles onthe electrode surface would prevent the two electrodes from makingdirect contact and would leave a thin continuous void that theelectrolyte could fill. Exposure of an edge of the two electrodesseparated by the spacers to a liquid or solution would draw the liquidor solution into the thin void, thereby filling this space withelectrolyte. The insulating spacer particles could be dispersed in theliquid or solution for placement. In this method, the solution or liquidcould be placed on the electrode surface by solvent casting, spincoating or other techniques. The two electrodes would be placed togetherwith the solvent and spacers already on one or both electrodes trappingthe electrolyte between the two electrodes. Direct electrode contactwould again be prevented by the spacers on the electrode surface. Theliquid could be any aqueous or non-aqueous electrolyte. The solventcould contain a dissolved polymer and inorganic salts. With thissolution, the solvent maybe evaporated leaving a polymer electrolytebetween the two electrodes.

In whatever way the thin layer of electrolyte is placed/depositedbetween the two electrode surfaces to complete the battery system, theelectrolyte will take advantage of the enhanced surface area of eachelectrode surface. The electrolyte will disperses itself into thefissures and crevices between the nanobasket structure, as shown in FIG.16( d), and onto the roughened nanostructure of the top surface of thenanobaskets taking advantage of the enhanced electrode surface area.

Three-Dimensional Nanobattery

The combination of nanostructured electrodes (the nanobaskets), currentcollectors (the nanowires) and thin-film electrolyte create a trulythree-dimensional nanostructured battery. Though theoreticalconfigurations and ramifications of a three-dimensional nanobattery havebeen discussed in the literature (W. Long Jeffrey, B. Dunn, R. RolisonDebra, S. White Henry, Chem Rev, 104 (2004) 4463-4492), and otherresearch efforts aimed at achieving it are under way, none of them haveyet yielded a complete working battery. The nanoscale three-dimensionalbattery architecture disclosed herein, however, has been reduced topractice and a successful charge/discharge sequence has been conducted,as shown in FIG. 18.

Whereas, the devices and methods have been described in relation to thedrawings and claims, it should be understood that other and furthermodifications, apart from those shown or suggested herein, may be madewithin the spirit and scope of this invention.

What is claimed is:
 1. A method of producing a nanobattery, said methodcomprising the steps of: providing a substrate having a plurality ofpores through said substrate, each of said pores having an edge at asurface of said substrate; depositing at least one material along saidedge of said pores of said substrate to form a plurality of nanobaskets,each of said nanobaskets having an internal cavity; depositing at leastone conductive material into said internal cavity of said nanobasketsand through said substrate to form a plurality of nanowires; andproviding a layer of electrolyte in contact with said nanobaskets,wherein said layer of electrolyte is intermediate of and in contact withexternal surfaces of said nanobaskets.
 2. The method of claim 1 furthercomprising the steps of: providing a cathode substrate having aplurality of pores, each of said pores having an edge at a surface ofsaid cathode substrate; depositing said at least one material along saidedge of each of said pores of said cathode substrate forming a pluralityof cathode nanobaskets having internal cavities; depositing said atleast one conductive material into said internal cavity of said cathodenanobaskets and through said pores of said cathode substrate to form aplurality of nanowires electrically connected to said cathode substrate;providing an anode substrate having a plurality of pores, each of saidpores having an edge at a surface of said anode substrate; depositingsaid at least one material along said edge of each of said pores of saidanode substrate forming a plurality of anode nanobaskets having internalcavities; depositing said at least one conductive material into saidinternal cavity of said anode nanobaskets and through said pores of saidanode substrate to form a plurality of nanowires electrically connectedto said anode substrate; providing said layer of electrolyteintermediate of said cathode nanobaskets and said anode nanobaskets; andmaking electrical contact between said plurality of nanowireselectrically connected to said cathode substrate and said plurality ofnanowires electrically connected to said anode substrate.
 3. The methodof claim 1 wherein said step of depositing said at least one materialalong said edge of said pores is accomplished by sputter-coating,chemical vapor deposition or pulsed laser method.
 4. The method of claim3 wherein said step of sputter-coating includes direct currentsputter-coating, radio frequency sputter-coating, magnetronsputter-coating and reactive sputter-coating.
 5. The method of claim 1further comprising step of depositing at least one additional materialto form a layered nanobasket structure.
 6. The method of claim 1 whereinsaid substrate is at least one of solid oxide, polymeric, ceramic,mineral or metallic materials.
 7. The method of claim 1 wherein saidsubstrate is a polycarbonate, carbon, silica, silicon or aluminamaterial.
 8. The nanobattery of claim 1 wherein said material depositedis an oxide, polymeric, ceramic, mineral or metallic material.
 9. Themethod of claim 8 wherein said material deposited is selected from thegroup consisting of tin oxide, lithium cobalt oxide, zinc oxide, copperoxide, titanium oxide, titanium dioxide, vanadium pentoxide, magnesiumoxide, silicon dioxide, carbon, silicon, nichrome, and hydroxyapatite.10. The method of claim 1 wherein said conductive material is copper orpoly(acrylonitrile).
 11. The method of claim 1 further comprising stepof depositing at least one additional material to form a layered capover said nanobasket.
 12. The method of claim 1 wherein said internalcavity of said nanobaskets further comprises an axial channel having anopen end and a capped end.
 13. The method of claim 12 wherein saidnanowires passes through said pores in said substrate, through said openend of said internal cavity, and into said channel of said internalcavity of said nanobaskets.
 14. The method of claim 1 wherein saidnanobaskets are capped nanobaskets each having said internal cavity. 15.The method of claim 1 wherein: said substrate is a plurality of cathodesubstrates and a plurality of anode substrates; said plurality ofnanobaskets is a plurality of cathode nanobaskets and a plurality ofanode nanobaskets; said plurality of nanowires is a plurality of cathodenanowires and a plurality of anode nanowires; said cathode nanowires arerespectively fabricated into said internal cavities of said cathodenanobaskets and through said pores of said cathode substrates; and saidanode nanowires are respectively fabricated into said internal cavitiesof said anode nanobaskets.
 16. The method of claim 15 wherein said layerof electrolyte is intermediate of an external surface of said cathodenanobaskets and an external surface of said anode nanobaskets.
 17. Themethod of claim 1 wherein said plurality of nanowires further comprisesa plurality of individually wired nanowires.
 18. The method of claim 17wherein each of said individually wired nanowires is in contact with aconductive contact plate.
 19. A method of fabricating athree-dimensional nanobattery, said method comprising the steps of:forming capped anode nanobaskets comprising axial anode channels;forming anode nanowires within said anode channels of said anodenanobaskets; forming capped cathode nanobaskets comprising axial cathodechannels; forming cathode nanowires within said cathode channels of saidcathode nanobaskets; and providing a layer of electrolyte intermediateof and in contact with an external surface of said anode nanobaskets andan external surface of said cathode nanobaskets.
 20. The method of claim19 further comprising forming said anode nanobaskets and/or said cathodenanobaskets by sputter-coating clusters of oxide, polymeric, ceramic,mineral and/or metallic materials.
 21. The method of claim 20 whereinsaid step of sputter-coating includes direct current sputter-coating,radio frequency sputter-coating, magnetron sputter-coating and reactivesputter-coating.
 22. The method of claim 20 wherein said materials aretin oxide, lithium cobalt oxide, zinc oxide, copper oxide, titaniumoxide, titanium dioxide, vanadium pentoxide, magnesium oxide, silicondioxide, carbon, silicon, nichrome and/or hydroxyapatite.
 23. The methodof claim 19 wherein said anode nanowires and/or said cathode nanowiresare copper or poly(acrylonitrile).
 24. The method of claim 19 furthercomprising electrically connecting said cathode nanowires to a cathodeconductive contact plate and electrically connecting said anodenanowires to an anode conductive contact plate.
 25. A method offabricating a three-dimensional nanobattery, said method comprising thesteps of: forming a plurality of cathode nanobaskets on a cathodesubstrate having a plurality of pores, each of said cathode nanobasketshaving an internal cavity; forming a plurality of individually wiredcathode nanowires in said internal cavity of said cathode nanobasketsand through said cathode substrate; forming a plurality of anodenanobaskets on a anode substrate having a plurality of pores, each ofsaid anode nanobaskets having an internal cavity; forming a plurality ofindividually wired anode nanowires in said internal cavity of said anodenanobaskets and through said anode substrate; providing a layer ofelectrolyte intermediate of said cathode nanobaskets and said anodenanobaskets; and making electrical contact between said cathodenanowires electrically connected to said cathode substrate and saidanode nanowires electrically connected to said anode substrate.
 26. Themethod of claim 25 further comprising the steps of: forming said cathodenanobaskets by depositing at least one material along an edge at asurface of each of said pores of said cathode substrate forming saidcathode nanobaskets; forming said cathode nanowires by depositing atleast one conductive material into said internal cavity of said cathodenanobaskets and through said pores of said cathode substrate; formingsaid anode nanobaskets by depositing said at least one material along anedge at a surface of each of said pores of said anode substrate; andforming said anode nanowires by depositing at least one conductivematerial into said internal cavity of said anode nanobaskets and throughsaid pores of said anode substrate.
 27. The method of claim 26 whereinsaid step of depositing said at least one material along said edge ofsaid pores of said cathode substrate and of said anode substrate isaccomplished by sputter-coating, chemical vapor deposition or pulsedlaser method.
 28. The method of claim 27 wherein said step ofsputter-coating includes direct current sputter-coating, radio frequencysputter-coating, magnetron sputter-coating and reactive sputter-coating.29. The method of claim 25 further comprising the steps of forminglayered cathode nanobaskets by depositing at least one additionalmaterial onto said cathode nanobaskets, and forming layered anodenanobaskets by depositing at least one additional material onto saidanode nanobaskets.
 30. The nanobattery of claim 25 wherein said materialdeposited is an oxide, polymeric, ceramic, mineral or metallic material.31. The method of claim 30 wherein said material deposited is selectedfrom the group consisting of tin oxide, lithium cobalt oxide, zincoxide, copper oxide, titanium oxide, titanium dioxide, vanadiumpentoxide, magnesium oxide, silicon dioxide, carbon, silicon, nichrome,and hydroxyapatite.
 32. The method of claim 25 wherein said conductivematerial is copper or poly(acrylonitrile).
 33. The method of claim 25further comprising the steps of forming a capped cathode nanobasket bydepositing at least one additional material over said cathodenanobasket, and forming a capped anode nanobasket by depositing at leastone additional material over said anode nanobasket.
 34. The method ofclaim 25 wherein said internal cavity of said cathode nanobaskets andsaid anode nanobaskets further comprises an axial channel having an openend and a capped end.
 35. The method of claim 25 further comprisingelectrically connecting said cathode nanowires to a cathode conductivecontact plate and electrically connecting said anode nanowires to ananode conductive contact plate.